Airborne antenna gimbal system

We are flying long range fixed-wing UAVs and want to improve our video downlink stability. At the moment we are in the 15 km range but we tend to lose connection when the plane banks, which is normal because the air antenna gets tilted, and the base station gets out of the most powerful zones of its radiation pattern. This is not good when the plane is doing loiter circling around an observation point because then it is always banking.

I am thinking that an easy fix would be to have a 1D gimbal (servo for more power), that keeps the antenna vertical all the time (only the banking axis need to be stabilised).

Has anyone already explored this idea? Would anyone be able to build this (by mod-ing some existing 1-axis camera gimbal for example)?